Part 4_two-stage Piston Compressor (1)

Equipment for Engineering Education

,QVWUXFWLRQ0DQXDO ET 500 Two-Stage Piston Compressor Unit

G.U.N.T. Gerätebau GmbH P.O. Box 1125 D-22881 Barsbüttel Phone (040) 670854-0 Fax (040) 670854-42

Piston Compressor Test Rig with PC-Data Acquisition

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

ET 500

Instruction Manual

Publication No.: 916.000 00B 500 12

11/96

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

Table of Contents 1

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1

Compressor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2

Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

2

System description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1

Construction of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.2

Process description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3

Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1

Installing the multifunction card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.2

Installing the software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

4.3

Starting the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

4.4

Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

5

Conducting the test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1

Measurements data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5.2

Taking the measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

5.3

Calculation of efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6

Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.1

Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

6.2

Work sheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

1

Introduction

1.1

Compressor

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

The compressor is part of a system for generation of compressed-air. Such systems are used where compressed air is needed as an energy source. This is particularly the case at work-sites where inflammable ga ses f orm a po t e n t i a l explosion danger (e.g. in mines, chemical industry, etc.), and also where the compressed air is utilised to substitute electric power. -

Mining: driving the machines.

-

Chemical industry: process control engineering.

-

Workshops, petrol stations: tools, paint spray guns, tyre inflators.

-

Assembly shops: automatic, pneumatic controls.

A compressed-air generation system consists essentially of:

5

4

2

7 1

6 8

3

compressed-air generation system

-

Compressor (1)

-

Drive motor (2)

-

Compressed-air tank (3)

-

Safety valve (4)

-

Pressure switch (electric drive)(5)

-

Pressure gauge (6)

-

Connecting pipes (7)

-

Chassis (8).

Air coolers, pressure reducers, water taps, etc. may also form a part of such systems. The compressor is the main component in any compressed-air generation system,

1 Introduction

1

ET 500

Piston Compressor Test Rig with PC-Data Acquisition where it is used to transform the supplied mechanical energy into an increase in air pressure.

1.2

Function

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

1

2

1 2 3 4 5 6 7 8

3 4

Discharge valve Intake valve Cylinder Piston Connectig rod Crankshaft Crank housing Oil sump

5 6

Piston Compressor

Compressors are machines which convey gaseous media (in this case, air) from low-pressure chambers into chambers with higher pressure. The energy supplied for this purpose by machines, e.g. electric motors or combustion engines, increases the pressure according to the intended use, but also warms the air. Part of the heat is returned to the ambient atmosphere by means of cooling fins. The side illustration shows the basic design of a reciprocating compressor. The volume of air in the cylinder is compressed by the upward movement of the piston and conveyed by means of a discharge valve into the pressure line.

7

On its downward stroke, the piston draws in fresh air via the intake valve.

8

A crank mechanism, consisting of crankshaft and connecting rod, produces the necessary upwarddownward movement of the piston from regular rotation. The oil required for lubricating the moving parts gathers in the oil sump.

1 Introduction

2

ET 500

Piston Compressor Test Rig with PC-Data Acquisition The process which takes place in a compressor can be illustrated by a so-called p,v- diagram.

p1

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v

Such p-v diagram shows the relation between the pressure in the cylinder and the corresponding cylinder volume. The side illustrations give an indication of the individual compression phases. The p,v-diagram has been turned clockwise through 90° to correspond to the piston stroke.

p2

-

Compression Starting from point 1, bottom dead centre (BDC), the piston compresses the air in the cylinder. The pressure increases with decreasing volume.

-

Discharge At point 2, the pressure in the cylinder has reached the pressure p2 in the pressure line. The discharge valve opens and the compressed air flows into the pressure line.

-

Re-expansion At point 3, the piston has reached top dead centre (TDC) and then reversed its direction. The discharge valve closes and the air left in the cylinder expands again. The pressure drops.

-

Intake At point 4, the pressure has dropped to the ambient pressure p1 with the result that the intake valve opens and fresh air flows into the cylinder. This process continues until the piston has reached bottom dead centre (BDC), where (at point 1) the entire procedure starts again.

1

p2

p1

2 v 1

p1

p2

3 2 v 1

p1

3 2

4 v

1 Introduction

p2

1

3

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

-

Two-stage compression If the pressure of the single-stage compression is increased, both the counter-pressure and temperature of the medium increase as well. The compression ratio is limited by the temperature at which the oil-gas mixture explodes. In the multi-stage compression, the medium is cooled down between the single stages. This decreases the volume losses, the powers on the rods and the required power. The cooling process allows a decrease of both the intake temperature and the intake volume of the second stage. In an ideal p-v diagram, the process of the second stage begins directly after the isentropic cooling of 1II and continues until the end pressure 2II. If this is a single-stage compression, the process would hold isentropically without stop until reaching the final pressure 2’. The difference between these two processruns is the work saving.

p p3

2II

3II

2’

Stage II

p2

4II 3

1II

2

Stage I p1 4

1 v

1 Introduction

4

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

2

System description

2.1

Construction of the system

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

The complete system is mounted on a welded square-steel-tube frame. -

Four castors for mobility and easy movement of the system.

-

Two castors are brakeable for secure standing.

-

The dimensions allow moving the system through normal door widths.

The apparatus contains a complete compressedair generation-system, including a two-stage builtin compressor and a compressed-air tank. D IN

0

D IN

16 bar

0

1,6 bar

Kl .1 ,6

Kl .1 ,6

-

Power supply needed to operate the system is 230V / 50Hz.

-

Low-noise operation by damped system bearings.

-

All measurement techniques and armatures are according to the latest industrial standards.

-

Large intake damper smoothens the volume flow and holds the measuring sensors.

DI N

0

16 bar Kl. 1,6

All electrical elements needed for operation are placed together in one switch cabinet.

2 System description

-

Main switch and emergency-stop switch.

-

Digital displays for all measured values.

-

Switch for compressor.

5

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

5

6

7

8

9

10

11

12

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

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3

13

2

1

17

16

15

14

1. Laboratory trolley

10. Orifice for Flow measurement

2. Drive motor

11. Differential pressure transmitter

3. Silencer

12. Control cabinet with digital displays

4. Pressure vessel 2nd stage

13. Resistance thermometer

5. Pressure transmitter

14. Pressure vessel and intercooler 1st stage

6. Pressure gauge

15. 1st compressor stage

7. Safety valve

16. Two cylinder piston compressor

8. Blow off valve

17. 2nd compressor stage

9. Intake vessel

2 System description

6

ET 500

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

2.2

Piston Compressor Test Rig with PC-Data Acquisition Process description The ET 500 Piston-Compressor Test-Rig is a twostage compressor system. The air is sucked into tank 1 via a measurement nozzle. Tank 1 serves as a moderation (stabilisation) zone in addition to supporting the measurement sensors for the intake stage. The intake volume is determined by the measurement nozzle. A small pressure tank is located between the first and second stages; it is used for the cooling stage. The compressed air is pressed into the tank 2 (pressure-air tank) through a cooling pipe. For the purpose of a stationary operating condition, the compressed air can be blown through an outlet valve equipped with an acoustic silencer. Safety valve and pressure switch complete the system.

3

Safety

M

PI

EI

PI 04 TI 04

TI 03

Tank 2

PI

TI 01

PI

PI 01

PD Tank 1 TI 02

PI 02

3 Safety

7

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

When operating the test rig, the following must be observed.

-

DANGER! Be careful when touching the electrical parts. Danger of electric shock. Pull the plug out of the mains. It should be dealt with by specialised personnel only.

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DANGER! Be careful of the hot surfaces and parts. Danger of burns. Let the unit cool down before service.

-

DANGER! Be careful of the drive. Danger of injuries from rotating parts. Protection cage must be always installed during operation.

3 Safety

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ET 500

4

Piston Compressor Test Rig with PC-Data Acquisition Operation In this section, the steps for a frictionless operation of the test rig are introduced. This instruction manual is valid only for the contemporary manufacturer’s unit.

4.1

Installing the multifunction card

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The card should be installed in the PC as follows:

4.2

-

Switch off the PC and pull the power cord.

-

Open the PC housing.

-

Find a free slot on the motherboard (make sure that the address 0320 HEX is not yet assigned in the computer.)

-

Insert the card and screw down.

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Close the PC housing.

Installing the software The software is installed on the PC with the aid of a user guidance system. Proceed as follows: -

Switch on the PC and start Windows.

-

Place the first installation disk in the floppy drive.

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Open the File Manager under Windows

-

Select the drive in which the installation disk has been inserted.

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Find the setup.exe file and activate with a double-click.

Installation is then carried out automatically. A special icon is generated under Windows, which is used to start the user software. Before starting the experiment, the following points should be observed.

4 Operation

9

ET 500

Starting the system

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

4.3

Piston Compressor Test Rig with PC-Data Acquisition

4 Operation

-

Place the system on a plane surface and secure it against rolling away by enabling the brakes.

-

Plug in the mains power supply.

-

Check the oil level when motor is OFF (also see service).

-

Turn the system ON by pulling the emergency-off switch and turning ON the main switch.

-

Turn the compressor ON. Turn the main switch ON , button I on the pressure switch ON (the switch is between the two upper pressure tanks). The compressor switches OFF at about 12 bar while the outlet valve being closed. It switches ON again when the pressure drops to about 10 bar. The ON/OFF pressure is adjustable on the pressure switch.

-

Turn the compressor OFF. Always press first the O on the pressure switch, so that the bleed valve is activated. The bleed valve vents the connecting pipes to the compressor, for smooth motor run. Turn OFF the main switch on the switch cabinet.

10

ET 500

4.4

Piston Compressor Test Rig with PC-Data Acquisition Maintenance Maintenance of the system is limited to the maintenance of the built-in compressor. To maintain the compressor, refer to instruction manual of the compressor made by KAESER.

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

The technical descriptions stated here are needed only for certain operating compressors. Within the frame of laboratory operations, the compressor is operated occasionally, so that the maintenance is limited to oil filling and checking the oil-level. Oil level and changing the oil Oil level: Before start-up, check the compressor for oilavailability. Viewing window

max

Check the oil level at the oil mark in the viewing window. Oil level must be at least up to the lower mark, otherwise add more oil up to the upper mark.

Changing the oil: Changing the oil only when the working temperature is on normal working level

Oil mark

-

Discharge the oil through the oil drain plug

-

For clenning the crankcase use only the recommended lubricating oil.

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Add oil through the oil inlet up to the mark.

min

ATTENTION! Do not forget to close the oil drain plug before adding oil. For periodical maintenance and oil specification, refer to section 6.1 Technical Data.

4 Operation

11

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

5

Conducting the test

5.1

Measurements data Pressure: The digital displays show the absolute pressure of the measurement positions in bar. The manometers mounted on the tanks show the overpressure of the measurement position in bar.

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

Differential pressure / intake volume: Venturi tube

The differenial pressure ∆p of a Venturi tube is proportional to the flow

Tank

. 2 ∆p V =Ad √  ρ . where V in m3/s, ∆p in Pa and ρ in kg/m3 and Ad=1,131∗10−4 m2 The density ρ of air depends on temperature and ambient pressure

∆p

100 ⋅ p0 ρ = 287 ⋅ (T + 273) with ρ in kg/m3, p0 in mbar and T in °C. The differential pressure ∆p is formed in the system from the environment pressure and the pressure in the smallest cross section of the Venturi tube. The output is displayed digitally (in mbar) after being transformed by the differential pressure transducer.

5 Conducting the test

12

ET 500

Piston Compressor Test Rig with PC-Data Acquisition Temperature: The temperatures are measured by means of four resistance thermometers. The values are displayed digitally. Transmitters converted the measured values to analog signals. Power:

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The power of the compressor motor is measured by means of a power transmitter. The measured value is also displayed digitally.

5 Conducting the test

13

ET 500

5.2

Piston Compressor Test Rig with PC-Data Acquisition Taking the measurements

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

The measurements listed should not be viewed as guideline or calibration values which must be adhered to in all circumstances. Deviations may occur to a greater or lesser extent in your own experiments, depending on the design of the individual components and ambient conditions. -

Turn the compressor ON (see section 4.3). If it does not run, the voltage-overflow switch, that is mounted directly on the motor, may have been switched off - press it again.

-

Let the system run until a constant pressure p3 has been reached. Set the desired final pressure with the outlet valve and note down the measurements.

p1 in bar

t1 in °C

p2 in bar

t2 in °C

t3 in °C

p4 in bar

t4 in °C

∆p in mbar

. V in l/min

Pel. in Watt

time 1) in min

0,99

23,0

3,4

127,1

58,8

11,7

151,6

7,4

239,51

2550

3

0,99

22,9

3.4

126,1

58,4

11,0

146,5

7,4

239,51

2510

3

0,99

22.8

3.3

125,1

58.0

10.0

141,5

7,5

241,12

2460

5

0,99

22,6

3.3

123,4

57,2

9,0

133,4

7,5

241,12

2400

5

0,99

22,3

3.2

121,0

56,1

8.2

124,2

7.6

242,73

2350

5

0,99

21,9

3.1

118,1

54,7

6,7

108,7

7,6

242,73

2240

5

1) Time needed for measurements to become steady

5 Conducting the test

14

ET 500

5.3

Piston Compressor Test Rig with PC-Data Acquisition Calculation of efficiency In order to determine efficiency of compressor, the hydraulic power must be calculated. The isothermal power of compression with intercooling is calculated as follows: . p Phydr. = p 1 ⋅ V 1 ⋅ ln p 4 1 . where p in Pa and V in m3/s

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

The efficiency is the ratio of hydraulic power to electric power input. P η = Phydr. el.

5 Conducting the test

15

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

ET 500

Piston Compressor Test Rig with PC-Data Acquisition

6

Appendix

6.1

Technical data Main dimensions length width height weight approx.

1520 750 1500 260

power supply

230 V, 50 Hz, 16 A

Compressor cylinders number of stages max. pressure: (used pressure Intake flow : speed maintenance intervals

mm mm mm kg

oil volume

2, V-shape 2 35 bar 12 bar) 250 l/min. 710 rpm first oil service after 50 operation hours, further services after 500 hours or after 1 year compressor oil conforming with DIN 51 506, group VG 30 (SAE 30) approx. 1.5 litre

Drive motor: power speed power supply

2,2 kW 3000 rpm 230 V, 50 Hz

oil specification

Intake vessel: capacity max. pressure Intercooler vessel: capacity max. pressure Pressure vessel: capacity max. pressure

6 Appendix

20 16

l bar

5 16

l bar

20 16

l bar

16

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ET 500

Piston Compressor Test Rig with PC-Data Acquisition Differential pressure transmitter: measuring range 0 - 10 output signal 0 - 10 auxiliary power 24

mbar V DC V DC

Pressure transmitter: measuring range 1x and 2x output signal auxiliary power

bar abs. bar abs. V DC V DC

0 - 1.6 0 - 16 0 - 10 24

Resistance thermometer with transmitter: type Pt 100 measuring range 0 - 200 °C output signal 0 - 10 V DC auxiliary power 230 V, 50 Hz Power transmitter: measuring range output signal auxiliary power

0 - 2500 W 0 - 10 V DC 230 V, 50 Hz

Digital display with power supply for transmitter: display 3 1/2 digit power supply for transmitter 24 V DC power supply 230 V, 50 Hz Multifunction card Analog inputs: Analog outputs: Digital inputs: Digital outputs: Counter:

16, 0 - 10 VDC 2, 0 - 10 VDC 8, TTL 8, buffered TTL 1, 16 bit

Software Runtime version of visual designer 4.0 completely configured. The software enables for online representation of measured values, graphically & numerically.

6 Appendix

17

p1 in bar

t1 in °C

p2 in bar

t2 in °C

t3 in °C p4 in bar

t4 in °C

∆p in mbar V. in l/min

All rights reserved G.U.N.T. Gerätebau GmbH, Barsbüttel 11/96

Pel. in Watt

Time in min

ET 500

6.2

Piston Compressor Test Rig with PC-Data Acquisition

Work sheet

Measurements table

6 Appendix

18